Group A Streptococcal diseases: For health professionals

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What health professionals need to know about Group A streptococcal diseases

Group A streptococcus (GAS) bacteria, Streptococcus pyogenes, are Gram-positive beta-hemolytic bacteria of which over 240 emm types (genotypes) have been identified.

GAS can be present on the skin and throat of asymptomatic carriers. It can also cause a range of clinical presentations in the form of invasive and non-invasive disease.

Clinical manifestations

Common presentations of GAS include:

  • Pharyngitis
  • skin infection such as impetigo
  • scarlet fever (less common presentation)

Occasionally, GAS causes invasive infections, which can be severe and possibly life threatening. This occurs when GAS infect sites that are usually sterile, such as:

  • blood
  • pleural fluid
  • bone or joint fluid
  • cerebrospinal fluid
  • deep muscle tissue

This can result in serious conditions, such as:

  • pneumonia
  • septicaemia
  • pyogenic arthritis
  • streptococcal meningitis
  • Streptococcal Toxic Shock Syndrome
  • necrotizing fasciitis (flesh eating disease)
  • puerperal sepsis (infection in the postpartum period)


GAS infections are treated with antibiotics. More information on the management of iGAS can be found in the guidelines for the Prevention and Control of Invasive Group A Streptococcal Disease.

Risk factors

Multiple studies have highlighted that the risk of invasive GAS disease is significantly associated with:

  • chronic diseases including
    • diabetes
    • lung disease
    • liver disease
    • heart disease
  • open wounds or breaks in the skin including:
    • cuts
    • burns
    • open sores
    • varicella infection
  • living in a crowded or unsanitary environment
  • substance abuse, including use of injectable drugs
  • weakened immune system, caused by factors such as
    • disease (HIV infection, AIDS)
    • cancer treatments (radiation and chemotherapy)
    • taking anti-rejection drugs following an organ or bone-marrow transplant
  • recent close contact with someone with a GAS or iGAS infection

Number of invasive Group A streptococcus cases in Canada

Invasive GAS (iGAS) became nationally notifiable in January 2000. Since the early 2000s, the incidence rate of iGAS has gone up steadily.

The rate has doubled from 2.7 cases per 100,000 people in 2004, to 6.2 cases per 100,000 people in 2016. Figure 1 shows the number of cases and incidence rates of iGAS in Canada by year from 2000-2016.

Figure 1

Text equivalent - Figure 1
Table 1: Number of invasive Group A streptococcus cases in Canada
Year Cases Incidence
2000 863 2.81
2001 830 2.68
2002 866 2.76
2003 1,039 3.28
2004 857 2.68
2005 1,025 3.18
2006 1,194 3.67
2007 1,420 4.32
2008 1,470 4.42
2009 1,355 4.03
2010 1,408 4.14
2011 1,644 4.79
2012 1,613 4.64
2013 1,661 4.72
2014 1,828 5.14
2015 1,893 5.28
2016 2,167 6.16

The age groups most affected are infants under 1 year of age and adults over 60 years of age and between 30 to 39 years of age. In 2016, age group-specific incidence rates for those age groups were:

  • 7.6 cases per 100,000 for infants under 1 year of age
  • 8.7 cases per 100,000 for adults over 60 years of age
  • 8.0 cases per 100,000 in adults between 30 to 39 years of age

The highest degree of change in incidence rates since 2000 occurred among adults between the ages of 20 to 24, 30 to 39 and 40 to 59 years.

Invasive Group A streptococcal disease in Canada

The Public Health Agency of Canada (PHAC) conducts annual national routine iGAS surveillance. This is done through the Canadian Notifiable Disease Surveillance System.

Basic demographic information is available, such as:

  • sex
  • age group
  • province or territory

The National Microbiology Laboratory conducts laboratory-based surveillance of the bacteria that causes GAS. Non-invasive GAS isn’t reported nationally, so PHAC does not have data on it.

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